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<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="beast.ref.boost__beast__flat_stream"></a><a class="link" href="boost__beast__flat_stream.html" title="flat_stream">flat_stream</a>
</h4></div></div></div>
<p>
        Stream wrapper to improve write performance.
      </p>
<h5>
<a name="beast.ref.boost__beast__flat_stream.h0"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__flat_stream.synopsis"></a></span><a class="link" href="boost__beast__flat_stream.html#beast.ref.boost__beast__flat_stream.synopsis">Synopsis</a>
      </h5>
<p>
        Defined in header <code class="literal">&lt;<a href="../../../../../../boost/beast/core/flat_stream.hpp" target="_top">boost/beast/core/flat_stream.hpp</a>&gt;</code>
      </p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
    <span class="keyword">class</span> <span class="identifier">NextLayer</span><span class="special">&gt;</span>
<span class="keyword">class</span> <span class="identifier">flat_stream</span>
</pre>
<h5>
<a name="beast.ref.boost__beast__flat_stream.h1"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__flat_stream.types"></a></span><a class="link" href="boost__beast__flat_stream.html#beast.ref.boost__beast__flat_stream.types">Types</a>
      </h5>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Name
                </p>
              </th>
<th>
                <p>
                  Description
                </p>
              </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  <span class="bold"><strong><a class="link" href="boost__beast__flat_stream/executor_type.html" title="flat_stream::executor_type">executor_type</a></strong></span>
                </p>
              </td>
<td>
                <p>
                  The type of the executor associated with the object.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <span class="bold"><strong><a class="link" href="boost__beast__flat_stream/next_layer_type.html" title="flat_stream::next_layer_type">next_layer_type</a></strong></span>
                </p>
              </td>
<td>
                <p>
                  The type of the next layer.
                </p>
              </td>
</tr>
</tbody>
</table></div>
<h5>
<a name="beast.ref.boost__beast__flat_stream.h2"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__flat_stream.member_functions"></a></span><a class="link" href="boost__beast__flat_stream.html#beast.ref.boost__beast__flat_stream.member_functions">Member Functions</a>
      </h5>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Name
                </p>
              </th>
<th>
                <p>
                  Description
                </p>
              </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  <span class="bold"><strong><a class="link" href="boost__beast__flat_stream/async_read_some.html" title="flat_stream::async_read_some">async_read_some</a></strong></span>
                </p>
              </td>
<td>
                <p>
                  Start an asynchronous read.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <span class="bold"><strong><a class="link" href="boost__beast__flat_stream/async_write_some.html" title="flat_stream::async_write_some">async_write_some</a></strong></span>
                </p>
              </td>
<td>
                <p>
                  Start an asynchronous write.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <span class="bold"><strong><a class="link" href="boost__beast__flat_stream/flat_stream.html" title="flat_stream::flat_stream">flat_stream</a> <span class="silver">[constructor]</span></strong></span>
                </p>
              </td>
<td>
                <p>
                  <br> <span class="silver">—</span><br> Constructor.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <span class="bold"><strong><a class="link" href="boost__beast__flat_stream/get_executor.html" title="flat_stream::get_executor">get_executor</a></strong></span>
                </p>
              </td>
<td>
                <p>
                  Get the executor associated with the object.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <span class="bold"><strong><a class="link" href="boost__beast__flat_stream/next_layer.html" title="flat_stream::next_layer">next_layer</a></strong></span>
                </p>
              </td>
<td>
                <p>
                  Get a reference to the next layer.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <span class="bold"><strong><a class="link" href="boost__beast__flat_stream/operator_eq_.html" title="flat_stream::operator=">operator=</a></strong></span>
                </p>
              </td>
<td>
              </td>
</tr>
<tr>
<td>
                <p>
                  <span class="bold"><strong><a class="link" href="boost__beast__flat_stream/read_some.html" title="flat_stream::read_some">read_some</a></strong></span>
                </p>
              </td>
<td>
                <p>
                  Read some data from the stream.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <span class="bold"><strong><a class="link" href="boost__beast__flat_stream/write_some.html" title="flat_stream::write_some">write_some</a></strong></span>
                </p>
              </td>
<td>
                <p>
                  Write some data to the stream.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <span class="bold"><strong><a class="link" href="boost__beast__flat_stream/_flat_stream.html" title="flat_stream::~flat_stream">~flat_stream</a> <span class="silver">[destructor]</span></strong></span>
                </p>
              </td>
<td>
                <p>
                  Destructor.
                </p>
              </td>
</tr>
</tbody>
</table></div>
<h5>
<a name="beast.ref.boost__beast__flat_stream.h3"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__flat_stream.description"></a></span><a class="link" href="boost__beast__flat_stream.html#beast.ref.boost__beast__flat_stream.description">Description</a>
      </h5>
<p>
        This wrapper flattens writes for buffer sequences having length greater than
        1 and total size below a predefined amount, using a dynamic memory allocation.
        It is primarily designed to overcome a performance limitation of the current
        version of <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">stream</span></code>,
        which does not use OpenSSL's scatter/gather interface for its low-level read
        some and write some operations. It is normally not necessary to use this
        class directly if you are already using <a class="link" href="boost__beast__ssl_stream.html" title="ssl_stream"><code class="computeroutput"><span class="identifier">ssl_stream</span></code></a>. The following examples
        shows how to use this class with the ssl stream that comes with networking:
      </p>
<h5>
<a name="beast.ref.boost__beast__flat_stream.h4"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__flat_stream.example"></a></span><a class="link" href="boost__beast__flat_stream.html#beast.ref.boost__beast__flat_stream.example">Example</a>
      </h5>
<p>
        To use the <a class="link" href="boost__beast__flat_stream.html" title="flat_stream"><code class="computeroutput"><span class="identifier">flat_stream</span></code></a> template with SSL streams,
        declare a variable of the correct type. Parameters passed to the constructor
        will be forwarded to the next layer's constructor:
      </p>
<pre class="programlisting"><span class="identifier">flat_stream</span><span class="special">&lt;</span><span class="identifier">net</span><span class="special">::</span><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">stream</span><span class="special">&lt;</span><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span class="special">&gt;&gt;</span> <span class="identifier">fs</span><span class="special">{</span><span class="identifier">ioc</span><span class="special">,</span> <span class="identifier">ctx</span><span class="special">};</span>
</pre>
<p>
        Alternatively you can write
      </p>
<pre class="programlisting"><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">stream</span><span class="special">&lt;</span><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span class="special">&gt;</span> <span class="identifier">ss</span><span class="special">{</span><span class="identifier">ioc</span><span class="special">,</span> <span class="identifier">ctx</span><span class="special">};</span>
<span class="identifier">flat_stream</span><span class="special">&lt;</span><span class="identifier">net</span><span class="special">::</span><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">stream</span><span class="special">&lt;</span><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span class="special">&gt;&amp;&gt;</span> <span class="identifier">fs</span><span class="special">{</span><span class="identifier">ss</span><span class="special">};</span>
</pre>
<p>
        The resulting stream may be passed to any stream algorithms which operate
        on synchronous or asynchronous read or write streams, examples include:
      </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
            <a class="link" href="boost__beast__file_mode.html" title="file_mode"><code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">read</span></code></a>,
            <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">async_read</span></code>
          </li>
<li class="listitem">
            <a class="link" href="boost__beast__file_mode.html" title="file_mode"><code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">write</span></code></a>,
            <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">async_write</span></code>
          </li>
<li class="listitem">
            <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">read_until</span></code>, <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">async_read_until</span></code>
          </li>
</ul></div>
<p>
        The stream may also be used as a template parameter in other stream wrappers,
        such as for websocket:
      </p>
<pre class="programlisting"><span class="identifier">websocket</span><span class="special">::</span><span class="identifier">stream</span><span class="special">&lt;</span><span class="identifier">flat_stream</span><span class="special">&lt;</span><span class="identifier">net</span><span class="special">::</span><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">stream</span><span class="special">&lt;</span><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span class="special">&gt;&gt;&gt;</span> <span class="identifier">ws</span><span class="special">{</span><span class="identifier">ioc</span><span class="special">,</span> <span class="identifier">ctx</span><span class="special">};</span>
</pre>
<h5>
<a name="beast.ref.boost__beast__flat_stream.h5"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__flat_stream.template_parameters"></a></span><a class="link" href="boost__beast__flat_stream.html#beast.ref.boost__beast__flat_stream.template_parameters">Template
        Parameters</a>
      </h5>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Type
                </p>
              </th>
<th>
                <p>
                  Description
                </p>
              </th>
</tr></thead>
<tbody><tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">NextLayer</span></code>
                </p>
              </td>
<td>
                <p>
                  The type representing the next layer, to which data will be read
                  and written during operations. For synchronous operations, the
                  type must support the <span class="bold"><strong>SyncStream</strong></span>
                  concept. For asynchronous operations, the type must support the
                  <span class="bold"><strong>AsyncStream</strong></span> concept. This type
                  will usually be some variation of <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">stream</span></code>.
                </p>
              </td>
</tr></tbody>
</table></div>
<h5>
<a name="beast.ref.boost__beast__flat_stream.h6"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__flat_stream.see_also"></a></span><a class="link" href="boost__beast__flat_stream.html#beast.ref.boost__beast__flat_stream.see_also">See
        Also</a>
      </h5>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
            <a href="https://github.com/boostorg/asio/issues/100" target="_top">https://github.com/boostorg/asio/issues/100</a>
          </li>
<li class="listitem">
            <a href="https://github.com/boostorg/beast/issues/1108" target="_top">https://github.com/boostorg/beast/issues/1108</a>
          </li>
<li class="listitem">
            <a href="https://stackoverflow.com/questions/38198638/openssl-ssl-write-from-multiple-buffers-ssl-writev" target="_top">https://stackoverflow.com/questions/38198638/openssl-ssl-write-from-multiple-buffers-ssl-writev</a>
          </li>
<li class="listitem">
            <a href="https://stackoverflow.com/questions/50026167/performance-drop-on-port-from-beast-1-0-0-b66-to-boost-1-67-0-beast" target="_top">https://stackoverflow.com/questions/50026167/performance-drop-on-port-from-beast-1-0-0-b66-to-boost-1-67-0-beast</a>
          </li>
</ul></div>
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